Persistence of carbamothioate herbicides in soils pretreated with butylate
1990
Field and laboratory studies were conducted to examine effects of prior butylate use on biodegradation of subsequent applications of butylate and four other carbamothioate herbicides. Bioassays were used to demonstrate reductions of butylate and EPTC activity in four soils preconditioned by annual butylate applications. Combining these herbicides with dietholate, an enzyme inhibitor, prolonged persistence and restored normal herbicidal activity. Expected herbicidal efficacy occurred in adjacent plots with no history of carbamothioate use. Prior applications of butylate resulted in cross-adapted degradation of EPTC but not vernolate, pebulate, or cycloate. When samples of Cecil soil were treated in the laboratory with 14C-butylate, evolution of 14CO2 was significantly higher from soils that had received repeated field applications of butylate. The use of 14C-herbicides could be used to predict problem soils and potential herbicide failure.
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